The present invention relates generally to edge card connectors, and more particularly to an edge card connector which has a plurality of generally U-shaped contacts which increase the performance of the connector.
Many electrical circuits, especially those used in the computer arts, are presently formed on one or more surfaces or levels of circuit boards, or similar substrates, to form separate circuits which may be added to computers or other electronic devices after initial manufacture thereof to improve the performance thereof. Whether such circuits are added during the initial manufacture or afterwards, these separate circuit boards must be reliably connected to the main computer printed circuit board, commonly referred to in the art as a "mother" board. The separate printed circuit boards are commonly referred to as "daughter" boards.
Connectors have been developed in the computer art which are designed for permanent installation on the mother board. These connectors contain a means for receiving the daughter board, such as a slot, to provide a connection between the mother board circuitry and the daughter board additional circuitry. These daughter boards are also descriptively referred to as "edge cards" because one side, or edge, of the card contains a plurality of relatively wide contact portions known as contact pads. The edge of the circuit card typically contains a plurality of these contact pads disposed thereon which extend laterally along one edge. One or both of sides of the edge card may contain such contact pads. This edge containing the contact pads is inserted into a slot of the connector which typically includes a number of electrical contact portions which may be similarly disposed along one or more sides of the connector slot in a manner to oppose the edge card contact pads. The connector contacts may typically include a tail portion, which projects from the connector for interconnection to the circuitry of the mother board positioned beneath or adjacent the connector. These ends are connected to the mother board by suitable means such as soldering to form an electrically conductive connection between the mother board and the edge card connector. Each connector contact further includes an edge card contact portion which is arranged within the card slot in a manner to abuttingly contact the edge card contact pads to provide an electrical connection between the edge card and the mother board.
Edge card connectors are well known in the art. One type of edge card connector is known as a low or zero-insertion force connector which is particularly suitable for receiving a single in-line computer memory module, commonly referred to as a "SIMM" module, to increase the memory capability of a computer. Such connectors are described in U.S. Pat. Nos. 3,848,952, issued Nov. 19, 1974 and 4,575,172 issued Mar. 11, 1986. In many of these low or zero insertion force edge card connectors, the connector contact terminals include two spaced-apart contact prongs, or arms, having opposing, spaced apart contact end portions. The edge card is inserted into the opening between the contact arms, contact pad edge first, and rotated for a predetermined angle until the edge card engages one or more mechanical latches. The spacing between the opposing contact arms is such that the contact pads of the edge card do not contact the contact arms of the connector with any appreciable normal force during insertion of the edge card.
Although reliable, this type of zero or low-insertion force edge card connector suffers from certain inherent disadvantages. Because such connectors require the edge card to be rotated, the spacing between adjacent connectors and other circuit board components must be sufficient to provide clearance for the insertion and rotation of the edge card. In instances where the rotatable edge cards are positioned adjacent each other, it may become necessary to remove one or more edge cards to remove a particular edge card. Finally, rotatable edge cards tend to warp because the contacts located adjacent the bottom edge of the card inherently exert a force tending to rotate the edge card back to its original position and latch mechanisms located at opposing ends of the card hold the card in an operative position. Over time and through cycles of insertion and removal, these forces tend to cause the card to warp which then causes a strain to be placed upon device I.C. leads which may cause failure thereof.
The other type of edge card connector known is commonly referred to as a "push-pull" edge card connector in which the edge card is inserted into the connector by pushing the edge card contact edge into the connector slot in a vertical direction. Removal of the edge card is attained by pulling it out of the slot or through the use of some type of urging mechanism. Such a "push-pull" type connector is described in U.S. Pat. No. 4,973,270 which issued Nov. 27, 1990. In such connectors, a plurality of contacts, or terminals, extend within the connector slot to provide the required contact surfaces for engagement when the edge card is inserted. However, certain parameters must be met in the construction of such connectors. For example, due to the translational insertion and removal nature of these connectors, it is desirable to keep the insertion forces low for ease of insertion and to minimize the wear on the edge card contact pads and the connector terminals.
Accordingly, a need exists for an edge card connector having stamped and formed resilient metal contact terminals disposed within a connector housing whereby a portion of the terminals are deflectable within the housing upon insertion of a circuit card into the connector.